Continuous flow solar disinfection system
This project aims to use solar radiation, an abundant resource in most developing countries, to disinfect water supplies. In developing countries water related diseases account for the majority of premature deaths which, in many cases, could be alleviated by providing an adequate supply of safe water. In such situations there are often neither the finances nor the resources to construct and maintain the energy and chemically intensive water treatment processes used in more industrialised countries. The purpose of this project is to develop a water treatment process which requires little or no energy, involving water flowing through a transparent pipe at the focal point of a compound parabolic reflector, optimally angled beneath the pipe for maximum sunlight capture to disinfect water supplies.
The continuous flow solar disinfection system has been designed with a village/rural application in mind, although the potential applications for the system are numerous. The basic principle of the system is shown below. The germicidal effects of UV radiation are well documented and solar radiation contains part of its electromagnetic spectrum as UV radiation (wavelength 100-400nm) of which only a fraction of the UV-B and UV-A wavelength bands reach ground level through the ozone layer. This system aims to optimise the use of both incident and reflected light from a reflector onto a clear pipe which carries the requisite water flow.
Initial research involved a series of laboratory scale trials, which were carried out using a solar simulator to establish the disinfection kinetics of the system with E. coli, S. typhimurium and V. cholera in a variety of different reactors. The laboratory scale reactors were then tested under real sunlight at Platforma Solar de Almeria in southern Spain, before refining the design of a full-scale prototype for trials at tropical latitude. (Figure - Small-scale solar photocatalytic disinfection reactor)
The first full-scale continuous flow solar disinfection system was installed in the village of Ndulyani in the Kitui district of Kenya to supply safe drinking water for approximately 600 people. This included the construction of a subsurface dam to store enough of the annual rainfall (which falls in a short rainy season) to supply the community for the rest of the year. The subsurface dam was selected in order to minimise evaporative losses and also provide some degree of protection from pollution. The water from the dam then flows by gravity into the solar disinfection system.
Project coordinator: Prof. Laurence Gill